[sdiy] RMP1b LFO rate and waveshape

[Yves Usson]

Hi

I think that one thing you can do is to connect the free lug of the 
rate pot
to a 1K resistor that is connected to the ground (this way your LFO 
will look
similar to that of the Wildcat). Second point, I think it's allways a 
good idea
to buffer the outputs with OPAs. Now, also the limit of such a simple 
design is
that you try to control at the same time the cyclic ratio and the rate 
and for
the lowest frequency you come to a point were the values of the RATE 
pot and the SYMETRY
pot interact...

Yves

Le 19 mai 06, à 11:12, James Dunn a écrit :

> I'm currently working on the LFO of the EFM Ring Modulator RMP1b.
> I included some diodes in the circuit for adjustable width (along with 
> a larger pot - 1M), also, I put a resistor (1k) in series with each 
> diode otherwise the waveform did some weird stuff at the far ends of 
> the width pot. So far, so good. The main issue is that at very low 
> frequencies, the sawtooth wave becomes more triangular - is there 
> something I can do to preserve the waveshape? I think it's the 
> capacitor in the feedback loop of the op-amp that causes this, and 
> when I connected the output to more than one point (on other modules), 
> the effect was less noticeable - I guess because the other modules are 
> sourcing more current from the cap, and therefore it drains quicker?
> Would a summing op amp fix this? The capacitor value is 470nf
> Any help appreciated.
>
> James
>
>
-------------------------------------------------
Yves Usson
email :       yves.usson at yusynth.net
web site :    http://yusynth.net